The present invention relates to a transmission arrangement for a vehicle. The invention also relates to a vehicle comprising such a transmission arrangement. The invention is applicable on vehicles, in particularly working machines such as e.g. wheel loaders, articulated haulers, dump trucks, etc. Although the invention will mainly be described in relation to an articulated hauler, it may also be applicable for other types of vehicles such as e.g. trucks.
In connection with transportation of heavy loads at construction sites or the like, a working machine is often used. The working machines may be utilized for transportations in connection with road or tunnel building, sand pits, mines, forestry and similar environments. Thus, the working machine is frequently operated with large and heavy loads in rough terrain and on slippery ground where no regular roads are present.
In order to fulfil the desired demands from the fields where the working machine is frequently operated, high performance of the vehicle gearbox is necessary. The gearbox is arranged for adjusting the speed and tractive effort of the vehicle in dependency of the specific driving scenario. The gearbox comprises a transmission arrangement and depending on the specific type of gearbox, the transmission arrangement may comprise e.g. ordinary gear sets with cylindrical gear wheels in meshed connection with each other or planetary gear sets comprising a respective sun gear, ring gear and a planet carrier, or a combination of ordinary gear sets and one or more planetary gear sets.
SE 527 108 describes a vehicle transmission arrangement, particularly suitable for working machines. The transmission arrangement in SE 527 108 comprises an input shaft and an output shaft. Five planetary gear sets are arranged between the input shaft and the output shaft for providing the desired gear ratios. Also, the transmission arrangement comprises three clutches and five brakes for achieving the desired gear shifts. Hereby, nine forward gears and four reverse gears are provided for the transmission arrangement in SE 527 108.
Although the transmission arrangement in SE 527 108 provides for a sufficient number of gears, the transmission arrangement is still in need of further improvements in terms of costs and functionality.
It is desirable to provide a transmission arrangement that enables fewer components to be used and has an improved gear shiftability in comparison to the prior art.
According to a first aspect of the present invention, there is provided a transmission arrangement for a vehicle, the transmission arrangement comprising a first, a second, a third, and a fourth planetary gear set comprising a sun gear, a planet carrier and a ring gear, respectively, wherein the transmission arrangement further comprises a transmission housing, an input shaft and an output shaft, wherein the ring gear of the first planetary gear set and the input shaft are operatively connected to each other; the planet carrier of the first planetary gear set and the planet carrier of the second planetary gear set are operatively connected to each other; the sun gear of the first planetary gear set and the ring gear of the third planetary gear set are operatively connected to each other; the ring gear of the second planetary gear set and the planet carrier of the third planetary gear set are operatively connected to each other, the planet carrier of the third planetary gear set and the sun gear of the fourth planetary gear set are operatively connected to each other; and the planet carrier of the fourth planetary gear set and the output shaft are operatively connected each other.
The wording “operatively connected to” should in the following and throughout the entire description be interpreted such that the components thereof are fixedly connected to each other, i.e. the rotational speeds of the components which are operatively connected to each other are equal. Hence, no engagement and disengagement mechanism or the like is arranged between the components that are operatively connected to each other and they can therefore not be disengaged from one another during operation. Accordingly, the planet carrier of the fourth planetary gear set is always connected to the output shaft of the transmission arrangement.
An advantage of the present invention is that, in comparison to the prior art, only four planetary gear sets are used in order to obtain a sufficient number of forward and reverse gears. This is advantageous both in terms of cost and packaging of the transmission arrangement since the number of components reduces the total cost for the transmission arrangement at the same time as it will be easier to fit the transmission arrangement to a vehicle. The engine compartment is an environment where it often is desirable to reduce the size of the components housed therein and the present invention hence reduces the size of the transmission arrangement by having one less planetary gear set in comparison to the prior art.
Moreover, by means of the present invention, nine forward gears and three reverse gears are obtainable, where the ratios and the steps for the different gears are considered to be able to appropriately operate e.g. a working machine to provide sufficient speed when necessary and sufficient torque when necessary. The ratio and step for the different obtainable gears will be described further below in relation to the detailed description of the present invention.
A still further advantage is that further additional gears and alternative gears in addition to the nine forward gears and the three reverse gears described above are obtainable. These additional gears and alternative gears will also be described further below in relation to the detailed description of the present invention.
According to an example embodiment, the transmission arrangement may comprise a first connecting mechanism for selectively connecting the input shaft to the sun gear of the second planetary gear set. The first connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
The wording “selectively connectable to” should be understood to mean that the components thereof are connectable to each other such that, when being connected to each other, the components have equal rotational speeds. Hence, the components may be directly connectable to each other or via another component.
According to an example embodiment, the transmission arrangement may comprise a second connecting mechanism for selectively connecting the sun gear of the third planetary gear set to the output shaft. The second connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
According to an example embodiment, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the ring gear of the second planetary gear set and to the planet carrier of the third planetary gear set. The third connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
According to an example embodiment, the transmission arrangement may comprise a fourth connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the sun gear of the third planetary gear set. The fourth connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
According to an example embodiment, the transmission arrangement may comprise a first locking mechanism for selectively locking the planet carrier of the first planetary gear set and the planet carrier of the second planetary gear set to the transmission housing. The first locking mechanism may, for example, be a brake arrangement, such as e.g. a wet or dry friction disc brake. Other alternatives are also conceivable such as e.g. a dog clutch. Hereby, the planet carrier of the first planetary gear set and the planet carrier of the second planetary gear set can be locked to the transmission housing such that rotation thereof is prevented.
According to an example embodiment, the transmission arrangement may comprise a second locking mechanism for selectively locking the ring gear of the third planetary gear set and the sun gear of the first planetary gear set to the transmission housing. The second locking mechanism may, for example, be a brake arrangement, such as e.g. a wet or dry friction disc brake. Other alternatives are of course also conceivable. Hereby, the ring gear of the third planetary gear set and the sun gear of the first planetary gear set can be locked to the transmission housing such that rotation thereof is prevented.
According to an example embodiment, the transmission arrangement may comprise a third locking mechanism for selectively locking the ring gear of the fourth planetary gear set to the transmission housing. The third locking mechanism may, for example, be a brake arrangement, such as e.g. a wet or dry friction disc brake. Other alternatives are also conceivable, such as e.g. a dog clutch. Hereby, the ring gear of the fourth planetary gear set can be locked to the transmission housing such that the ring gear is prevented from rotating.
According to an example embodiment, the stationary gear ratio of each one of the first, second, third and fourth planetary gear sets may be negative. An advantage is that single planet wheels are used, which reduces cost and gear mesh losses.
According to a second aspect of the present invention there is provided a method for controlling a transmission arrangement, the transmission arrangement comprising a first, a second, a third, and a fourth planetary gear set comprising a sun gear, a planet carrier and a ring gear, respectively, wherein said transmission arrangement further comprises a transmission housing, an input shaft and an output shaft, wherein the ring gear of the first planetary gear set being operatively connected to the input shaft; the planet carrier of the first planetary gear set being operatively connected to the planet carrier of the second planetary gear set; the sun gear of the first planetary gear set being operatively connected to the ring gear of the third planetary gear set; the ring gear of the second planetary gear set being operatively connected to the planet carrier of the third planetary gear set; the planet carrier of the third planetary gear set being operatively connected to the sun gear of the fourth planetary gear set; the planet carrier of the fourth planetary gear set being operatively connected to the output shaft; wherein the transmission arrangement further comprises: a first connecting mechanism for selectively connecting the input shaft to the sun gear of the second planetary gear set; a second connecting mechanism for selectively connecting the sun gear of the third planetary gear set to the output shaft; a third connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the ring gear of the second planetary gear set and to the planet carrier of the third planetary gear set; a fourth connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the sun gear of the third planetary gear set; a first locking mechanism for selectively locking the planet carrier of the first planetary gear set and the planet carrier of the second planetary gear set to the transmission housing; a second locking mechanism for selectively locking the ring gear of the third planetary gear set and the sun gear of the first planetary gear set to the transmission housing; and a third locking mechanism for selectively locking the ring gear of the fourth planetary gear set to the transmission housing; wherein for at least one of the gears of the transmission arrangement, the method comprises the steps of: positioning three of the locking and connecting mechanisms in an engaged state; and positioning four of the locking and connecting mechanisms in a disengaged state.
Hereby, the majority of elements are disengaged for the different gears of the transmission arrangement, which thus may increase durability of friction components etc.
According to an example embodiment, the method may comprise the step of positioning the second and the third locking mechanisms, and the first connecting mechanism in an engaged state when engaging a first forward gear. According to an example embodiment, the method may comprise the step of positioning the second and the third locking mechanisms, and the third connecting mechanism in an engaged state when engaging a second forward gear. According to an example embodiment, the method may comprise the step of positioning the third locking mechanism, and the first and third connecting mechanisms in an engaged state when engaging a third forward gear. According to an example embodiment, the method may comprise the step of positioning the third locking mechanism, and the second and the third connecting mechanisms in an engaged state when engaging a fourth forward gear. According to an example embodiment, the method may comprise the step of positioning the third locking mechanism, and the first and the second connecting mechanisms in an engaged state when engaging a fifth forward gear. According to an example embodiment, the method may comprise the step of positioning the third locking mechanism, and the second and the fourth connecting mechanisms in an engaged state when engaging a sixth forward gear. According to an example embodiment, the method may comprise the step of positioning the first, second and fourth connecting mechanisms in an engaged state when engaging a seventh forward gear. According to an example embodiment, the method may comprise the step of positioning the second locking mechanism, and the first and the second connecting mechanisms in an engaged state when engaging an eighth forward gear. According to an example embodiment, the method may comprise the step of positioning the second locking mechanism, and the second and the third connecting mechanisms in an engaged state when engaging a ninth forward gear.
Thus, well defined forward gears are provided for the transmission arrangement.
According to an example embodiment, the method may comprise the step of positioning the second and the third locking mechanisms, and the fourth connecting mechanism in an engaged state when engaging a first additional forward gear having a gear ratio higher than the gear ratio of the first forward gear.
Hereby, a further forward gear is provided which has a higher gear ratio than the gear ratio of the first forward gear, thus enabling for a forward gear with higher output torque capabilities. Also, when shifting from the first additional forward gear to either one of the first forward gear and the second forward gear, only one of the connecting and locking mechanisms are changed from an engaged state to a disengaged state, and only one of the connecting and locking mechanisms are changed from a disengaged state to an engaged state.
According to an example embodiment, the method may comprise the step of positioning the second locking mechanism, and the second and the fourth connecting mechanisms in an engaged state when engaging a second additional forward gear having a gear ratio between the gear ratios of the seventh and eighth forward gears.
Hereby, a further gear is arranged between the seventh and eighth forward gears which provides for an additional step between the seventh and eight gears. A gear shift from the sixth forward gear to the second additional forward gear provides a smaller step compared to changing from the sixth to the eighth forward gear and only one of the connecting and locking mechanisms are changed from an engaged state to a disengaged state, and only one of the connecting and locking mechanisms are changed from a disengaged state to an engaged state. In a similar manner, when changing from the ninth forward gear to the second additional forward gear a smaller step is provided compared to changing from the ninth to the seventh forward gear, and only one of the connecting and locking mechanisms are changed from an engaged state to a disengaged state, and only one of the connecting and locking mechanisms are changed from a disengaged state to an engaged state.
According to an example embodiment, the method may comprise the step of positioning the first and the third locking mechanisms, and the first connecting mechanism in an engaged state when engaging a first reverse gear. According to an example embodiment, the method may comprise the step of positioning the first and the third locking mechanisms, and the fourth connecting mechanism in an engaged state when engaging a second reverse gear. According to an example embodiment, the method may comprise the step of positioning the first and the third locking mechanisms, and the second connecting mechanism in an engaged state when engaging a third reverse gear.
Thus, well defined reverse gears are provided for the transmission arrangement.
It should be readily understood that the above defined example embodiments of forward and reverse gears may be combined in any suitable combination.
Further effects and features of the second aspect of the present invention are largely analogous to those described above in relation to the first aspect of the present invention.
According to a third aspect of the present invention there is provided a control unit configured to control a transmission arrangement, the transmission arrangement comprising a first, a second, a third, and a fourth planetary gear set comprising a sun gear, a planet carrier and a ring gear, respectively, wherein said transmission arrangement further comprises a transmission housing, an input shaft and an output shaft, wherein the ring gear of the first planetary gear set being operatively connected to the input shaft; the planet carrier of the first planetary gear set being operatively connected to the planet carrier of the second planetary gear set; the sun gear of the first planetary gear set being operatively connected to the ring gear of the third planetary gear set; the ring gear of the second planetary gear set being operatively connected to the planet carrier of the third planetary gear set; the planet carrier of the third planetary gear set being operatively connected to the sun gear of the fourth planetary gear set; the planet carrier of the fourth planetary gear set being operatively connected to the output shaft; wherein the transmission arrangement further comprises: a first connecting mechanism for selectively connecting the input shaft to the sun gear of the second planetary gear set; a second connecting mechanism for selectively connecting the sun gear of the third planetary gear set to the output shaft; a third connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the ring gear of the second planetary gear set and to the planet carrier of the third planetary gear set; a fourth connecting mechanism for selectively connecting the sun gear of the second planetary gear set to the sun gear of the third planetary gear set; a first locking mechanism for selectively locking the planet carrier of the first planetary gear set and the planet carrier of the second planetary gear set to the transmission housing; a second locking mechanism for selectively locking the ring gear of the third planetary gear set and the sun gear of the first planetary gear set to the transmission housing; and a third locking mechanism for selectively locking the ring gear of the fourth planetary gear set to the transmission housing; wherein for at least one of the gears of the transmission arrangement, the control unit is configured to position three of the locking and connecting mechanisms in an engaged state; and position four of the locking and connecting mechanisms in a disengaged state.
Effects and features of the third aspect of the present invention are largely analogous to those described above in relation to the first and second aspects of the present invention.
According to a fourth aspect of the present invention there is provided a vehicle comprising a prime mover and a gearbox, wherein the gearbox comprises a transmission arrangement according to any one of the embodiments described above in relation to the first aspect of the present invention.
Effects and features of the fourth aspect of the present invention are largely analogous to those described above in relation to the first, second and third aspects of the present invention.
Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.